Photonic crystal lasers juiced

Photonic crystal materials contain tiny, regularly spaced air holes or semiconductor rods that make it possible to channel light within microscopic spaces. The material promises to enable all-optical computer circuits and could also be used to make ultra low-power light sources, including lasers.

Researchers have made lasers from microscopic cavities in photonic crystals that act as reflectors to intensify the collisions between photons and atoms that lead to lazing, but these lasers have been optically-pumped, meaning they are driven by other lasers.

Researchers from the Korean Advanced Institute of Science and Technology and the Electronics and Telecommunications Research Institute in Korea have made a photonic crystal laser that is driven by electric current. The device could eventually be used as a source of single photons for quantum cryptography and communications devices, as an ultra low-power laser, and as a light source for photonic crystal circuits.

The room-temperature device produced light at the telecommunications wavelength of 1.5 microns using 260 millionths of an amp of electrical current. Laser pointers typically use several hundred thousandths of an amp.

The laser consists of a 50-micron-wide photonic crystal suspended above a surface. A one-micron-high semiconductor post connects the surface to the center of the crystal. A micron is one thousandth of a millimeter. The post serves as an electrode that carries electrical current into the device.

The challenge in making an electrically-driven photonic crystal laser was configuring the post to conduct current efficiently while minimizing the post's impact on the cavity's optical properties, according to the researchers.

The work appeared in the September 2, 2004 issue of Science.